Oil rate control for burners



March 16, 1943. w. A. REED y OIL RATE CONTROL FOR BURNERS Filed Sept.26, 1940 by www@ His Attorf'neg.

MEIN Ouml 'Patented Mar. 16, 1943 OIL RATEv CONTROL FOR BURNEBS WilliamA. Reed, West Caldwell, N. J., assignor to General Electric Company, acorporation oi' New York Application September 26, 1940, Serial No.358,387 Claims. (Cl. 158463) This invention relates to oil burners,particularly of the air pressure atomizing nozzle type in which both oiland air are separately supplied from a variable pressure oil and airsupply source to an atomizing nozzle wherein the two are mixed anddischarged to establish flame. This general type of air pressureatomizing nozzle oil burner is disclosed in the Lum Patent 2,072,761 andthe Wotring Patent 2,124,443, both of which disclose and claim improvedmeans for regulating the rate of ow of oil to the atomizing dischargeorifice of the burner nozzle.

The principal object of the present invention is to provide an improvedoil rate regulating method and apparatus for oil burners -of the airpressure atomizing nozzle type.

A specific object is toy vary the oil rate by changing the size ofan-orice in the air supply line for the air pressure oil atomizingnozzle and -l also changing the pressure at which both oil and air aresupplied to the nozzle with the oil always flowing through an orice of axed size located adjacent the atomiz'ing nozzle tip.

A preferred embodiment'of the invention is illustrated schematically inthe accompanying drawing in ,which Fig. 1 shows the improvements of theinvention applied to an oil burner ofY the improved conversion typeadapted to be used with furnaces of various types and sizes as describedin the application of Aldo Macchi, Serial No. 320,557, led February 24,1940; Fig.,2 is an enlarged sectional view of the oil and air mixing andpressure atomizing nozzle which is shown as of the improved typedescribed in the application of Aldo Macchi, Serial No. 320,558, iiledFebruary 24, 1940; Fig. 3 is an enlarged sectional view showing thepreferred form of the improved air ow regulating means employed in thepresent invention to control therate of the supply of oil to the burnernozzle; Fig. 4 is a diagram illustrating the manner in which the air andoil pressures drop as they separately pass from a common pressure sumpchamber to the burner vnozzle and Fig-5 is a chart showing the variationin oil rate of the burner obtained by means of the present invention;Figs. 6 and 7 are different modifications of the air ilow controlorifice 20 shownvin Fig. 3 that are employed to vary the oil rate.

p As shown in Fig. 1 of the drawing, the burnerair pressure oilatomizing nozzle i0 is located within the burner combustion airdischarge nozzle II which may be sealed into the wall of the combustionchamber of the furnace I2 as illustrated.- i

Oil under pressure is supplied to the atomizing nozzle I0 from thebottom of the oil and air pressure equalizing sump chamber I5 throughthe oil supply pipe I6.- As shown in Fig. 2, a thin walled sharp edgedorifice Il of predetermined size is mounted in the nozzle I0 at the endof the oil supply pipe I6 in order to meter the ow of oil and alsoprovide viscosity compensation in the manner described and claimed inthe above Lum and Wotring patents.

Air under pressure is supplied from the upper part of the sump I5through an air metering orifice 20 which may be varied in size and.preferbly is located for convenience in changing to different sizeorifices adjacent to the sump I5. The air passing through the oriilce 20is con- Y ducted through the air supply pipe 2I to the nozzle I0. Bothoil and air are pumped into the sump I 5 under pressure by an electricmotor driven oil and air pumping mechanism 30 which also drives theblower '3| to supply combustion air to the air nozzle II. A sumppressure regulator 35 is provided for varying the air pressure withinthe sump I5 as described hereinafter.

Fig. 2 shows the internal construction of the air pressure oil atomizingnozzle I0. In the nozzle I0, the oil supplied under pressure throughpipe i6 discharges through the oil flow regulating orice Il and mixes inthe chamber I8 with the air supplied under pressure through pipe 2 I.Thus the mixing of the oil and air occurs under pressure. The mixturepasses from thev mixing chamber I8 through the radial passage I9 and isdischarged under pressure at the nozzle discharge orifice 22 which hasmaximum and minimum pressure limits variable with the mixture foreiective atomization of the oil. When the atomizlng pressure at orifice22 falls below the minimum effective limit, the oil and air mixture maydrizzle out of the discharge orifice 22 with insumcient velocity toproduce eiective oil atomization. Under these conditions imperfectcombustion and carbonization of the burner inherently results. On theother hand, when the oil and air mixture is discharged from the nozzleA22 at pressures above the maximum effective limit, the velocity of themixture may become materially greater than the rate of propagation offlame. In this case the flame will be driven so far from'the nozzle aslikely to be extinguished `or at least a noisy, rapidly pulsating, andunstable llame may result. v v

In accordance with the present invention, the rate of oil flow throughthe metering oil oriilce Il to the. atomizing nozzle I0 may be regulatedthrough a series of values by changing the size of the air meteringorifice 20 and thereby inversely varying the rate of oil flow throughthe oil metering orifice I1 and the pressure oi' the atomizing airsupplied to the nozzle I while the asi-gees v pressure drop occurs asthe air flows through the pipe 2l to the mixing' chamber I8 as indicatedsump pressure regulator 35 is adjusted to vary -v 'supplied from the topportion of the sump I5 through the air outlet port 24 formed in the base25 of the electric motor driven oil and air pressure supply pumpingmechanism having the pumping part 30a thereof suspended from base 25within the sump I5 to supply oil and air under pressure thereto. The airmetering orifice is as shown in the preferred form of a special T-connection which is .screw threaded into the base in communication withthe air outlet port 24. As indicated in Figs. 6 and '7, a plurality ofT- connections with different size air metering oriiices formed thereinare provided for selectively obtaining different oil rates. Thepreferred form of connection T orifices is employed so as to permit thescrew plug 28 at one end thereof to lbe removed and an air pressuregauge temporarily connected -as indicated in dotted lines to indicatethe pressure in the sump I5 appliedto the orifice.

The pressure in sump I5 is controlled by the automatic regulator 35.This consists of the needle valve 36 which controls the air bypass port31 which may be connected to the air inlet port 38 of the pumping port30a of the electric motor driven-oil and air pumping mechanism as shown.The needle valve 36 is operated by the bellows 39 which is responsive tothe air pressure in the sump air outlet port 24. The spring 40 isadjusted by screw 4| to vary the air pressure to which bellows 39responds. Thus when the air pressure in the sump I5 increases, thebellows,

39 responds to move the needle valve 36 farther away from the port atthe entrance yto the air bypass 31. This enables more air to pass fromthe sump I5 through the outlet port 24 and into the by-pass passage 31,thereby reducing the air pressure in the sump I5. Conversely, Vwhen theair pressure in sump I5 decreases, the bellows 39 responds to move theneedle valve 36 closer to the 'port at the entrance to the by-pass 31thereby restricting the flow of by-pass air and causing the air pressurein sump I5 to increase.

Fig. 4 is a diagrammatic illustration of the relative pressure dropsoccurring in the oil and air supply system to the nozzle mixing chamberI8. Line A represents the initial pressure of both the oil and the airin sump I5. As the oil leaves the sump I5 and passes through pipe I6 tothe oil metering orifice I1, a slight gradual reduction in the pressureon the oil occurs due to friction loss in the pipe as indicated by lineB. In passing through the oil metering orice I1 the pressure materiallydrops as indicated at AI.

The air on leaving sump I5 is subject to an initial rapid pressure dropcorresponding to the velocity head as indicated at CI witha furthergradual loss in pressure as the air passes through the outlet port 24 asindicated at C2. v When the' air passes through the restricted` airmetering orifice 20 a rapid drop in pressure occurs as indicated at C3.Then a still further gradual at C4.

"I'he pressure differential effective to produce ow of oil through theoil metering orifice I1 is the difference in pressure aty the end of theoil pressure line B on one side of orifice I1 and the air pressure lineC on the other side of orifice I1. Likewise the pressure available toblow the air and oil mixture from the mixing chamber I8 and through thenozzle discharge orifice 22 is the difference .between the pressure atthe end of the air pressure line C and the zero pressure line. Thus, inaccordance with the present invention by varying the size of the airmetering orifice 20, the air, pressure drop indicated by C3 may be`varied with a corresponding inverse variation of the differentialpressure across the oil flow orifice I1 and the atomizing pressure Vo'fthe nozzle I0. When the size of the air metering orifice 20 is varied,there necessarily results a variation in the ratio of oil to air in themixing chamber with aconsequent variation in the mixture projectedthrough the atomizing nozzle orifice 22. The oil and air mixture-issuesfrom this nozzle orifice 22 during operation as a fog. Thus the more airthat is supplied to the mixture, the less oil can issue from the nozzletip. Conversely, the -more oil that is supplied, the less air can issuefrom the nozzle tip. Such variations in the ratio of oil and air issuingfrom the atomizing nozzle tip will change the effective minimum andmaximum atomizing pressures required to provide for satisfactoryatomization and combustion of the oil.

In practicing the invention in a preferred form, variations in the oilrate have been obtained as indicated in the following data table whichtabulates the variations in the size of the air meter- 'ing orifice, thecorresponding variations in sump pressure, corresponding variations inthe air line pressure below the air metering orifice, and also Theseresults were obtained by selectively employing the diiferent'size airiiow control orifices 20a and 20h shown 'schematically in Figs. 6 and 7with the length of the air pipe 2l about 20 inches and with an insidediameter of .150 inch and the oil supply pipe I6 of a length of about 23inches with an inside diameter of .150 inch. The oil metering orice I1had a diameter of .0465 inch which is a #56 drill size.

diameter of 1/8 inch.

In the above table it will be noted that at the 1.08 oil rate and alsothe 1.30 oil rate, the observed oil and air pressure differential on theopposite sides of the'oil metering orifice seem to be zero. But sincethe oil did fiow through vthe oil orice at the rate indicated, thereinuertlitxl must have .been suiiicient diierential to gi -head`oLat3ut.01 lb. necessary to make the oil iiow at the indicatediratethrough the'I'he disf charge orifice 22 of the burner nozzle had a diameter of theorice inthe air supply line inif. `herently changes the ratio of oil andair in the orice l1. As indicated in the above table,` the observedpressure differential across the oil orifice l1 materially increases atthe higher oil rates.

The chart of Fig. 5 shows the variation in oil rate obtained with the.three different size air orices indicated schematically in the drawingas 20, a and 20h in the air supply line according to the data given inthe above table and shows the relation between the oil rate and the sump.pressure within the maximum and minimum effective atomizingl pressurelimits of the nozzle for each of the three air orices. with the 1%"diameter a'ir metering'oriiice a sump pressure of 2.5 lbs. projided theminimum eilective atomizing pressure at the nozzle discharge orifice 22below which the flame became unsatisfactory. By raising `the sumppressure to 3.25 lbs., an increase in the oil rate to 1.30 gallons perhour was obtained with the maximum effective atomizing pressure at thenozzle discharge orifice 22 above which the flame became too unstableand noisy for satisfactory operation. In order toV provide higher oilrates, the

-air metering oriiice diameter was reduced to .104

inch. With this reduced size of air oriice in the system and with a sumppressure of 2.25 lbs. to give the minimum eiective atomizing pressure atthe nozzle, the oil rate was 1.59 gallons per hour. Upon increasing thesump pressure to Thus 3 lbs., the oil rate was correspondinglyincreasedto 1.89 gallons per hour with the atomizing pressure at the nozzledischarge orifice 22 at its maximum effective limits. To obtain stillhigher oil rates, the air oriiice diameter was then reduced to .082square inch and the sump pressure increased to 4.5 lbs. This resulted inan oil rate of 2.6 gallons per hour with the pressure at the nozzledischarge orice 22 at the minimum effective atomizing limits. Then' whenthe sump pressure was increased to 6.5 lbs'. so as to bring the pressureat the nozzle discharge oriiice 22 up to the maximum eiective limits,the oil rate became 3.06 gallons per hour.

Thus by means of the present invention a progressively increasing seriesof oil rates was obtained by variation of the size of the air meteringoriiice with corresponding variations of ber having separate oil and airsupply connec- 4 the sump pressure so as to maintain the nozzleatomizing pressure within eiective atomizing limits. The atomizingnozzle discharge curves X, Y and Z shown in Fig. 5 indicate thevariations in the oil rate that were obtained. Points a and b on curve Xcorrespond respectively with the 1.08 gallons per hour oil rate obtainedwith the 2.5 lbs. per square `inch sump pressure and the 1.30 gallonsper hour oil rate obtained with the 3.25 lbs. per square inch sumppressure. Both of these rates were obtained with the 13g-inch diameterorifice in the air supply line.

Points c and d on curve Y correspond respectively with the 1.59 gallonsper hour oil rate obtained with the 2.25 lbs. per square inch sumppressure and the 1.89 gallons per hour oil rate obtained with the 3.0'lbs.` per square inch sump pressure, both of which were obtained withthe .104-inch diameter orice in the air supply line.

The points e and f on curve Z correspond Arespectively'with the 2.65gallons per hour oil rate with the 4.5 lbs. per square inch sumppressure and the 3.06 gallons per hour oil rate with the 6.5 lbs. persquare inch sump pressure. In this case the diameter of the oricein theair line was .082.

As previously pointed out, variation in the mixture discharged from theburner atomizing nozzle. The changes in the slope of the curves X, Y andZ indicate such variations in the ratio oi oil and air in the mixturedischarged from the nozzle orice 22.

What I claim as new Vand desire to secure by Letters Patent of theUnited States, is:

1. In an oil burner, in combination, means providing a chamber tormixing oil and air under pressure and having a thin walled oil owregulating inlet orifice for discharging oil into said f chamber,discharge means connected with said mixing chamber for discharging saidoil and air mixture under pressure to atomize the oil, means including avariable pressure oil and air supply chamber having separate oil and airconnections communicating with the opposite sides of said oil flowregulating inlet orice for supplying oil and air under pressure to saidmixing` chamber, variable air flow regulating means including aplurality of diierent size orifice elements, each adapted for mountingin said air pressure supply connection for correspondingly varying therate of oily flow through said oil regulating inlet orice and thepressure drop -of the air supplied to said mixing chamber, and

pressure control means having an adjustable element for regulating thepressure in said oil and air supply chamber to vary the pressure of themixture supplied from said mixing chamber to said discharge means andcorrespondingly vary the rate of oil iiow through said oil regulatinginletorice.

2. In an oil burner, in combination, means providing a chamber formixing oil and air under pressure, discharge means connected with saidmixing chamber for discharging said mixture under pressure toatomize theoil, means including a variable pressure oil andair supply chamtionswith said mixing chamber with a thin walled oil ow regulating orifice atthe discharge end of said oil pressure supply connection, and means forregulating the rate of oil ow through said regulating orice includingselectively variable air flow orice means in said air pressure 3. In anoil burner, in combination a burner l nozzle having a chamber for mixingair and oil under pressure and means for discharging said oil and airmixture under an atomizing pressure variable between predeterminedmaximum and minimum effective operating limits, oil and air pumpingmeans having a sump for maintaining the air and oil under a commonpressure therein, separate oil and air supply connections extendingbetween said sump and said nozzle, a thin walled oil ilow regulatingorifice in said oil connection for discharging oil into said chamber,variable orifice means for selectively varying the pressure drop in saidair supply connection to correspondingly vary the rate of oil iiowthrough said regulating oriiice, and means for varying said sumppressure to maintain said atomizing at the oil inlet'tosaid/mixing'chamber, oil and v air pumping means having a sump formaintaining the oil and air under a common pressure therein, separateoil and air supply connections extending between said sump and nozzle,and a plurality of different size orifice means, each adaptedselectively to be mounted in said air supply connection remotely fromsaid nozzle for selectively determining the pressure drop in said airsupply connection to correspondingly determine the rate of oil ilowthrough said regulating orifice and means for varying said sump pressureto maintain said atomizing pressure within said maximum and minimumlimits.

5. In combination, an oil burner atomizing nozzle having an oil land airmixing chamber provided with a thin walled oil flow regulating inletorifice, oil and air supply means for said nozzle including an oil andair pressure equalizing sump having separate oil and air supplyconnections with the opposite sides of said orifice, and means forvarying the oil rate of said nozzle including a variable flowrestricting orifice means in said air supply connection and -a pressureregulator for varying the pressure of said sump.

WILLIAM A. REED.

